Guides and tricks

Charging the GPS clock while in use


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The range of a GPS watch is an important aspect for all users, the less times you find your training partner is out of battery the happier your existence will be (first world problems). But for some of you it's not that important, it's crucial.

All of you who participate in ultra distance races will find in this article the information you were looking for, because nowadays there is nothing in the market that is able to withstand the entire event.

Yes, all manufacturers have incorporated different methods to extend battery life with energy saving functions, but if we reduce the recording rate we will always lose information. We will always be interested in recording GPS data per second, and in those conditions even the longest running watches will not go beyond 20-24 hours. And that's considering optimal conditions.

The most common option is to reduce the GPS logging rate, which can give us many more hours of use depending on the model, even reaching 200 hours. But that will affect the reliability of the GPS signal, not only leaving a poor quality track of your race (and it's not a workout you'll repeat tomorrow to be able to record correctly), but while you're doing the test you won't have valid data on pace or distance (unless you use external sensors) and of course it will affect route navigation.

There is a second option to consider, charging the watch battery while you are running. This is something that can work quite well but not all models support it, and in case they do, it may not be comfortable because of the position of the connector or the design of the charging cable.

Clocks that allow charging while in use

Below is a list of models that allow charging while still recording the activity, as well as continuing to display data on the screen. Those with the thumb upwards allow more or less comfortable charging thanks to the format of their charger, while those with the thumb downwards must be charged in another way, without being on the wrist.


  • Epix
  • Phoenix
  • Phoenix 2
  • Phoenix 3
  • Fenix 3 HR
  • Forerunner 230
  • Forerunner 235
  • Forerunner 630
  • Forerunner 735XT
  • Vivoactive
  • Vivoactive HR
  • Phoenix 5
  • Fenix 5S
  • Fenix 5X
  • Forerunner 935
  • Vivoactive 3


  • Polar V800
  • M400
  • M430


  • Ambit
  • Ambit2
  • Ambit3
  • Spartan Sport
  • Spartan Trainer
  • Spartan Ultra
  • Suunto 9

Remember, all those listed allow you to save the activity and Those that are less recommended are because of the shape of its connector. To give an example, the Garmin Fenix 3 is a perfect candidate to be used in this way because its connection, besides being flat, is anchored to the watch very securely by the four grip points.

Charge GPS clock while using 1

This would not be possible with the Garmin Fenix 5 because it uses a smaller, more convenient, direct-to-rear connector that is not suitable for this use.

Garmin Fenix 5 - Unpacking


The same applies to the other models on the list that are not recommended to do this (Polar M400, Garmin Vivoactive 3, etc.).

There are also some models that allow you to record the activity but do not show the information on screen (only the loading screen), such as Forerunner 310XT and Forerunner 910XT. And finally the 920XT that would allow it, but not directly and it would be necessary to perform a trick in order to do so.

Of course, if you have to charge in this way and you are using the optical pulse sensor of those models that integrate it, you will no longer have a pulse register because it will not be in contact with the skin.

One last note is that for most Garmin models it is necessary to enable the "Garmin" USB mode in the System menu. By default the enabled mode is "Mass Storage".

Which cable to use

You can use the same cable that you use to charge your phone, but you may want to find an extra one to avoid damage to your main cable. If you are in the middle of a race and are moving around stones, branches or trees, you may want to make sure that the damaged cable is not your original cable, but one you have bought for the occasion. There are many manufacturers that have compatible cables for Garmin, Suunto or Polar.

Another problem may be the length of the cable, usually one meter. If you are going to carry the battery in your hand while you are charging the watch, it may be a little uncomfortable. You have the option of winding it around your wrist, but perhaps a cleaner and more practical option is braid the wire to reduce its length while making it more rigid.

Recommended battery

When choosing a battery to accompany you on your long runs, you don't have to go for too complicated solutions or look too far. Keep in mind that watches usually have small batteries between 200 and 400 milliamps. more basic and economical batteries are 2,600mAh with enough energy to fully recharge the watch about 8 times.

I assume that most of you will have such a battery, although perhaps in most cases they will be of considerably greater capacity and, of course, with greater volume and weight.

Whether you have a battery that is too big or not, I recommend that you opt for a compact size battery from a reputable manufacturer. I recommend the products of Anker as they are of good quality at a fairly reasonable price.


And specifically for this particular use, the Anker PowerCore 5,000mAh offers a very compact size and twice the capacity of the most basic models, so you can also recharge your mobile phone in an emergency.

So here it is, a list of the models that you can use in your next ultra trail. I hope you found the information useful. If you think I've forgotten a model or if you have any additional tricks for ultra distance racing, let us all know using the comments below.

And with that... thanks for reading!

Eduardo Mateos

I've been surrounded by electronic devices of all kinds for more than 25 years. Using them, testing them, taking them apart and dissecting them. Long distance triathlete: I swim, run and cycle for a long time. Maybe too much.

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  1. Hello!
    Congratulations on your page, your work is great.
    I'm weighing the purchase of an Ambit3 Peak.
    I understand from your article that it would be possible to carry it on your wrist. It is comfortable to wear it while carrying, just like the Phoenix 3 you show?
    Thank you very much.

    1. It is not so comfortable, because it is still a "clamp" that is anchored on one side of the watch. And it does not have a very firm anchorage, so with the movements of the arms it can move and stop charging. But it is perfectly feasible.

  2. What a pity that in garmin for the fenix 5 they changed the type of connection, for me they have screwed up since the loader of the fenix 3 is the best of all, that little they think about us at the time of making these things, they only think about selling units and that's it.

    1. I personally like the new design of the connector very much, and I won't deny that I find it very comfortable when dealing with several Garmin watches, but it also has some negative points as in this case.

      What I find strange is that no one has created a connector that looks like the one used on the Fenix 3 with a 3D printer.

  3. I had already thought about this once, although I really have hours to spare xD. I see us with the backpack with a water tube on one shoulder and a cable on the other.

  4. Hi Edu! One question, when I start charging the Fenix 3 during very long workouts or ultras, I get a window by default that shows the battery, the % of charge and the current time.

    At the time I didn't hit the key and I thought that even though I was still recording the activity, I couldn't see the data in real time.

    A salute and thank you for your crack work!

    1. Try changing the connection mode. Right now I don't have a Fenix 3 handy, but with the rest of the Garmin, it's no problem.

  5. I tried right now with the 735XT to charge while I'm in an activity, and the activity stops automatically, and not only that, but the watch goes to a charging screen and when you stop charging the activity has already disappeared. So I'm afraid it can't be charged during the activity.

      1. The thing is that I have looked for this mode in the garmin and there are no eggs to find it, that is, in configuration > System, there is no connection mode option.

        1. That's right, I'm seeing that option removed in favor of "intelligent interpretation" by the watch.

          I am testing it right now and it responds perfectly, if I connect it to an external battery the watch simply charges but without changing the connection mode, as intended.

          1. Tested and working! ;). It's true. As there is no option to change the mode by hand, the change is automatic. If you connect it to the PC it doesn't work, but if you connect it to a charger only, then it does. Interesting especially thinking of Ironman during the bike segment.

  6. Hi, I've done several ultras, ranging from 12 to 31 hours, with my Garmin Forerunner 610. The charging connector is perfect for wearing while running. When you put it on charge you can only see the time and battery percentage but it still records the activity perfectly.

  7. Hello

    I have a Garmin 920xt and the article does not explain the "trick" to poder charge the watch during the activity, maybe it is what is said about the USB mode, but I can not find that option in the system menu ....

    Has anyone been able to use that model during the activity by charging the battery and having it record data?

    Thank you very much!

  8. Hello, then to do ultras it compensates more the suunto spartan ultra than the suunto 9, because of charging while using it?

    1. You can load them either way, but Suunto 9's range functions are a very important plus. If you're going to be pulling out quite a lot of range I would certainly go for the 9 and opt for this possibility if it's really necessary.

  9. Hi, I have a Suunto Ambit2R and when I connect it to the power bank, the charge comes out for a few moments and after about 5 seconds it stops charging.
    What am I doing wrong. What could cause me to stop carrying?

    1. Check that the connector is clean and well placed, normally when there are interruptions of this type it is because of dirt on the contact pins.

  10. Hello, can the fenix 5s be loaded while in use? Can the data be viewed on the clock screen?

    1. With the Fenix 5S apply everything you see in the text about the Fenix 5. It's the same watch, but a little smaller.

  11. "And finally the 920XT which would allow it, but not in a direct way and it would be necessary to perform a trick to poder do it." What would be the trick?


    1. I have already updated with the link to the video, for some reason it was not published correctly at the time.

  12. Hi eduardo. with regard to the polar m400. why does it have the thumb down? is it impossible to charge it while you run and continue with the gps reading? or is it because you can not wear it on your wrist while charging, due to the place of its connector? I ask because today I tried to charge it in the middle of a walk and the gps data screen was gone and in its absence, the screen appeared with the message "charging". and pressing the button to change the screen, the reading of time and distance continued. but I do not know how reliable will be the data it collects, since the watch is not on the wrist.
    Thank you.

    1. Yes, as I put above are those that do not allow the load more or less easily. And given the fragility of the connector of the M400 the truth is that it would not move too much while it is in load ...

  13. Thank you Eduardo! The information you provided was of great value to me. I have had a Garmin Phoenix 5x pro for about 4 years and as expected, the battery life is no longer as efficient as it was at the beginning. I was looking into buying a Fenix 7x pro solar because of its great battery life. I run ultras and I do high mountain in Argentina and I like to track well detailed routes. Due to import problems in my country, this watch does not enter and if it were imported it would be worth $ 1.200.000 in my country's currency (a fortune). I followed your advice to the letter, bought a 2,600 mAh Anker for $ 8,000 and was able to recharge while still recording my activities without problems! For that matter, I take the watch off my wrist and hang it from a carabiner on the front of my hydration vest or backpack. That way the cable doesn't bother me and the charger is usually placed in a small pocket. Charging from 5% to 100% takes me about 1 hour. Sensational! I saved a lot of money. Thank you very, very much!

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